class Cat():
    def sayWho(self):
        print("我是小猫")
        pass
class Dog():
    def sayWho(self):
        print("我是小狗")
        pass
class Pig():
    def sayWho(self):
        print("我是小猪")
        pass
class Duck():
    def sayWho(self):
        print("我是鸭子")
        pass
class Person():
    def sayWho(self):
        print("我是人类")
        pass

def intruduction(who):
    for item in  who:
        item.sayWho()
        pass
list1=[Cat(),Dog(),Pig(),Duck(),Person()]
intruduction(list1)